Humans have an extraordinary ability to manipulate and traverse the physical world using complex motor behaviors while also incorporating the use of tools to extend or amplify portions of their body. In order to do this successfully, the brain must construct and continuously update an internal model of the physical self and its relation to the environment by integrating multisensory inputs from both the body and its surroundings, which can then be used to generate intentional movements to explore and interact with the physical world. This internal model of the physical self includes: establishing a boundary between the body and the world, knowing the configuration of that body relative to the world, and, when using tools, temporarily incorporating such tools into the internal representation of the body. This process is thought to occur within the parietal-motor network, a set of brain areas that, when damaged by stroke or trauma, can lead to a range of perceptual and movement deficits. The amazing repertoire of behaviors that the human parietal-motor network can produce evolved from simpler networks present in our early ancestors; these networks have been modified and enhanced in concert with alterations of the body and other brain areas over millions of years of evolution. As a result, there are subsets of movements and motor abilities, such as hand-to-mouth feeding, which are present in extant mammals that shared a common ancestor with humans. Those mammals that are more closely related likely share a greater number of common features of both brain organization and behavior than more distantly related species. The goals of this proposal are to gain insight into those features that are shared across mammals, and to bridge the gap in our understanding between two common animal models that are more distantly related to one another, rodents, such as rats, and primates, such as macaque monkeys. This will be done by studying the parietal-motor network of tree shrews, a close phylogenetic relative to both orders and thus and ideal intermediate model between rodents and primates. Findings will be compared to those of parallel ongoing studies in rats and primates within the Krubitzer laboratory, and other laboratories. Neuroanatomical tracing and intracortical microstimulation (ICMS) techniques will be employed to define areas in posterior parietal cortex (PPC) in tree shrews that may be homologous to areas found in primates and rodents, and motor and posterior parietal areas will be deactivated using a novel cooling chip technique to examine the functional dynamics of motor and parietal areas on the execution of movements. Using a combination of connectional and functional data from tree shrews along with parallel comparisons from primates and rodents will provide information on what features of the parietal-motor network are common among them, and likely present in humans. By establishing these common features, a foundation from which appropriate interpretations of data from either rodents or primates for the human condition can be made.